Solvent extraction apparatus

ABSTRACT

A solvent extraction apparatus is provided wherein the materials being extracted flow countercurrently along the walls of a rotating cylinder in contact with each other. The apparatus may be either of the batch or the continuous type. Preferably a helical path is provided.

United States Patent 1 1 1111' 3,709,665

Coulson [451 Jan. 9, 1973 54] SOLVENT EXTRACTION APPARATUS 3,117,031 1/1964 Griffiths ..23/269 x [76] Inventor: Dill M. Coulson, 884 Colorado FOREIGN PATENTS OR APPLICATIONS Ave., Palo Alto, Calif. 94303 38/4648 6/1960 Japan ..23/269 [22] Filed: June 15, 1970 [21] AppL NW 46,122 Primary Examiner-Norman Yudkoff Assistant Examiner-S. J. Emery AttorneyEckhoff, Hoppe, Slick, Mitchell & Ander- [52] U.S. Cl. ..23/269, 23/2705, 23/310 son [51] Int. Cl. ..B0ld 11/04 [58] Field of Search ..23/269, 270.5, 3 I0, 309 [57] ABSTRACT A solvent extraction apparatus is provided wherein the [56] References Cited materials being extracted flow countercurrently along UNITED STATES PATENTS the walls of a rotating cylinder in contact with each other. The apparatus may be either of the batch or the 2,705,594 Brewer X continuous type Preferably a helical path is provided 2,199,928 5/1940 Van Wirt.... .....23/269 X 3,457,708 7/1969 Deford ..23/269 X 6 Claims, 5 Drawing Figures SOLVENT EXTRACTION APPARATUS SUMMARY OF THE INVENTION The present invention relates to a solvent extraction apparatus which gives several theoretical stages in a relatively small piece of equipment. Ordinarily solvent extraction devices consist of a number of chambers and occupy a substantial amount of space. The device of the present invention is a small, compact apparatus and is particularly useful in small sizes where it occupies only a small amount of space on a laboratory bench. However, the device can also be made in larger sizes for production use.

The apparatus comprises a cylindrical chamber which is rotated on its long axis. Preferably the cylinder is vertical and the chamber has a helical path defined therein as by cutting a thread in the cylinder. The liquids to be contacted to flow countercurrently along the walls of the vessel in a helical path and extraction takes place in the interface between the two liquids. The action of the centrifugal force is such that the liquids are confined to the grooves and also are prevented from mechanically mixing.

Although other centrifugal solvent extraction devices have been suggested in the past, normally these are fairly cumbersome, expensive devices and do not lend themselves to a small scale use. The device of the present invention is simple and compact. It is easily built as a continuous or batch extractor.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a diagrammatic showing of the paths which the liquids take in flowing through an apparatus embodying the present invention.

FIG. 2 is a horizontal section of an apparatus embodying the present invention, adapted for batch extraction.

FIG. 3 is an enlarged sectional view of a wall portion of FIG. 2 illustrating the method by which extraction takes place.

FIG. 4 is a horizontal section of an apparatus for continuous extraction.

FIG. 5 is an enlarged section of a portion of the apparatus of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, which is a diagrammatic view showing the method in which the present invention operates, a heavy liquid is introduced through line 5 and flows on the outside helical path as at 7. A relatively light immiscible liquid is introduced through line 9 and follows a path parallel and countercurrent to that of the heavy liquid but inside the path of the heavy liquid as at 11. Although not shown in this view, the helix is rotated so that the liquids are kept separated and also kept against the walls of the extraction vessel. The number of turns which the liquid makes will depend on the degree of extraction desired. After the desired amount of extraction has taken place, the light liquid is removed through line 13 while the heavy liquid is removed through line 15.

FIGS. 2 and 3 show a practical embodiment of the present invention adapted for batch extraction. In this embodiment a cylindrical vessel generally designated 17 is provided which is mounted on a shaft 19 which is driven by a suitable prime mover such as an electric motor 21. The hollow vessel 17 has a central, generally cylindrical chamber or hollow open center 23 with a thread-like groove 25 cut therein. Instead of having the thread cut, a separate partition member might be employed to define a helical path. At the bottom of the chamber an enlarged portion or charnfer 27 is provided. Near the top of the vessel a light liquid passage 37 is provided together with a collector ring 39 for the light liquid. To operate the apparatus, the large portion 27 is first charged with the lighter liquid while heavier liquid is gradually fed in through pipe 31. The heavier liquid 41 displaces the lighter liquid, the lighter liquid 43 moving up while the heavier liquid moves down through the helical groove. The heavy liquid collects in 27 as is shown. Thus, one starts out with all of the light liquid at 27 and ends up with all of the heavy liquid in 27 with the light liquid being completely displaced.

Although not illustrated, a third liquid may be added at some intermediate point of the extraction apparatus.

Referring now specifically to FIG. 3, a section through the extractor wall is shown. The extractor generally designated 17 has the groove 25 as heretofore described and the heavy liquid 41 and the light liquid 43 flow down counter-currently along this groove in a parallel path. The two liquids do not mix and extraction takes place at the interface 45 between the two liquids.

In FIGS. 4 and 5 a similar apparatus is shown except here the apparatus is adapted for a continuous extraction. The device consists of a cylinder 50 adapted to be rotated by shaft 52, the cylinder having a helical groove 54 as heretofore described. An outlet 56 is provided near the top for a light liquid with an accompanying collector ring 58. An outlet for heavy liquid is provided by passage 60 near the bottom with its corresponding collector ring 62. The passage 60 is provided with a baffle 61 permitting the light liquid to pass by the outlet pipe 60 without being trapped thereby as is shown in detail in FIG. 5. Inlet pipes 64 and 66 are provided, pipe 64 being utilized for the introduction of a heavy liquid near the top of the apparatus while the pipe 66 is utilized for the introduction of light liquid substantially at the bottom of the chamber.

Extraction takes place as previously described with the heavy liquid 41 descending along the spiral groove while the light liquid 43 ascends over the surface of the heavy liquid.

It is believed apparent from the above that I have provided a small, compact extractor and one which occupies a minimum amount of space. A large degree of extraction is thus provided in a very compact apparatus.

Although two specific embodiments of the invention have been illustrated, it will be understood by those skilled in the art that many modifications can be made in the structures shown without departing from the spirit of this invention.

In the embodiments illustrated, a helical thread is provided since this gives a long extraction path. However, a cylindrical vessel can be used. Also, it is preferred that the cylinder be rotated on a vertical axis, but this is not necessary.

I claim:

1. A liquid-liquid solvent extraction apparatus comprising in combination:

a. a cylindrical vessel having a single vertical wall mounted for rotation on its vertical axis, said vessel having a hollow, open center closed at its bottom,

b. means defining a helical path on the inside of the wall extending from the top of the wall to the bottom of the wall,

c. inlet means at the top of said vessel for introducing a heavy liquid along the inside of the wall at the top of said vessel and into said helical path for flow therealong,

d. means at the bottom of said vessel for introducing a light liquid along the inside of the wall at the bottom of said vessel and into said helical path,

e. outlet means at the top of said vessel for removing a light liquid from near the top of said vessel,

f. means connected with said vessel for rotating said vessel about its vertical axis at a predetermined speed such that the heavy liquid is held in contact with the inside of the wall of said vessel and is constrained to move in the helical path and the light liquid is held in contact with the heavy liquid and is constrained to move in the helical path, with the heavy liquid and light liquid held in separate and distinct layers, solely by centrifugal force, so that said liquids move in countercurrent flow along the wall of said cylindrical vessel in said helical path without mixing and wherein extraction takes place solely at the interface between the two liquids. 2. A liquid-liquid solvent extraction apparatus as in 5 claim 1, wherein outlet means is at the bottom of said vessel for removing a heavy liquid from the bottom of said vessel.

3. A liquid-liquid solvent extraction apparatus as in claim 2, wherein a baffle means is at said outlet for heavy liquid to insure that only heavy liquid is removed from said vessel through said outlet and enabling the light liquid to pass by the heavy liquid outlet.

4. A liquid-liquid solvent extraction apparatus as in claim 3, wherein the light and heavy liquid outlets are IS in the side of said wall at the top and bottom thereof,

respectively.

5. A liquid-liquid solvent extraction apparatus as in claim 1, wherein an enlarged chamber is at the bottom of said vessel in open communication with the hollow, open center of said vessel, said chamber initially filled with a light liquid, said heavy liquid flowing downwardly along said wall from the heavy liquid inlet at the top of said vessel and displacing said light liquid from said chamber.

6. A liquid-liquid solvent extraction apparatus as in claim 1, wherein the means defining the helical path comprises a helical thread or groove cut in the wall. 

2. A liquid-liquid solvent extraction apparatus as in claim 1, wherein outlet means is at the bottom of said vessel for removing a heavy liquid from the bottom of said vessel.
 3. A liquid-liquid solvent extraction apparatus as in claim 2, wherein a baffle means is at said outlet for heavy liquid to insure that only heavy liquid is removed from said vessel through said outlet and enabling the light liquid to pass by the heavy liquid outlet.
 4. A liquid-liquid solvent extraction apparatus as in claim 3, wherein the light and heavy liquid outlets are in the side of said wall at the top and bottom thereof, respectively.
 5. A liquid-liquid solvent extraction apparatus as in claim 1, wherein an enlarged chamber is at the bottom of said vessel in open communication with the hollow, open center of said vessel, said chamber initially filled with a light liquid, said heavy liquid flowing downwardly along said wall from the heavy liquid inlet at the top of said vessel and displacing said light liquid from said chamber.
 6. A liquid-liquid solvent extraction apparatus as in claim 1, wherein the means defining the helical path comprises a helical thread or groove cut in the wall. 